1. Field of the Invention
The present invention relates to a method and apparatus for measuring solder bumps formed on a semiconductor module such as LSI, on TAB (Tape Automated Bonding), and the like.
2. Description of the Related Art
FIGS. 1A to 1C illustrate the structure of a semiconductor module 1 having a number of solder bumps. FIG. 1A is a diagram showing the overall structure of the semiconductor module. FIG. 1B is an enlarged view of a bump area A of the semiconductor module and illustrates a relative position of solder bumps. FIG. 1C is an enlarged view of a bump 10 (corresponding to B in FIG. 1A).
A number of solder bumps 10 are formed on the bottom of the semiconductor module 1. Each bump is used for connection to a wiring board on which the semiconductor module 1 is mounted. The semiconductor module 1 is of a square shape having a side length of, for example, 10 mm. Solder bumps 10 are formed on the surface 8 at a pitch of, for example, 450 xcexcm, totalling in number to 23xc3x9723.
Each bump 10 is generally spherical as shown in the enlarged view of FIG. 1C.
There is no apparatus for automatically measuring a height of a number of spherical bumps to date. Therefore, height is measured visually by using a focus-of-depth microscope or the like.
Works (to be measured) such as semiconductor modules formed with a number of bumps are positioned at a later process on a wiring board, and bumps are heated and melted in a heating furnace to be connected to the wiring board.
In order to reliably connect the bumps, it is necessary to correctly measure a height of each bump at its apex.
The size of each bump is required to have predetermined values so that adjacent bumps and wiring connections are prevented from being electrically shorted.
However, it is very difficult to measure heights of a number of bumps correctly and in a short time.
One of the inventors of this invention has proposed techniques of measuring a height of a work by using an optical beam, as disclosed in JP-A-2-80905.
It is an object of the present invention to provide a method and apparatus capable of measuring bumps on a work correctly at high speed.
The measuring method of this invention comprises the steps of: mounting a work to be measured on a table, the work having solder bump rows; detecting a reference bump from the solder bumps by using a laser optical micro head; scanning the solder bump rows with the optical micro head and detecting a shift amount of a mount posture of the work; correcting the shift amount of the mount posture of the work by scanning the table; and measuring height positions of apexes of all the solder bumps with the optical micro head.
The method of the invention further comprises the steps of calculating a regression plane formed by the apexes of the solder bumps and calculating a relative apex position of each solder bump relative to the calculated regression plane. The method of the invention further comprises the steps of calculating a standard deviation of relative heights and judging from the standard deviation and the apex height of each bump whether the work is defective or not.
A measure apparatus of this invention comprises: a table for placing thereon a work to be measured, the work having solder bump rows; moving means for moving the table in a two-dimensional plane in two perpendicular axis directions; rotating means for rotating the table about a vertical axis; inclining means for inclining the table; a laser optical micro head mounted on the table to be movable in the vertical axis direction; a personal computer for recording data measured by the optical micro head in the form of digital data; controlling means for controlling the table and the optical micro head; a personal computer for calculating a height position of an apex of each solder bump in accordance with the data measured by the optical micro head; a display screen for displaying the calculated results; and a printer for printing out the calculated results.
According to the present invention, a work is measured by scanning a light spot by the optical micro head. Therefore, the drive speed can be changed depending upon a necessary measurement precision and the size of the work, so that high speed, high precision, and versatility can be realized for various applications.
As above, the invention provides a method and apparatus for measuring heights of all of a number of bumps formed on a work such as an LSI and judging whether the work is good or not. The invention is applicable to works having highly dense bumps expected in the future.